Cocobolo Tree Farm 
Central America's Premier Nursery
Sweet lemon, Limon dulce
Known as sweet lime, lemon limonsón or Rome ( Citrus × limetta ), more lemon-like in size, skin thickness and color, is distinguished mainly by its very low astringency and by the characteristic nipples at both ends.
http://es.wikipedia.org/wiki/Lima_(fruta)
Additional Information
References
http://www.victoriananursery.co.uk/Mediterranean_Sweet_Lemon/
http://en.wikipedia.org/wiki/Citrus_limetta
